1. Field of the Invention
The present invention relates to an air intake control device of an engine, and more particularly, to an air intake control device of a fuel injection engine having throttle valves.
2. Description of the Related Art
In a general type of internal combustion engine, such as an in-vehicle engine, a piston is disposed in a cylinder block so as to move reciprocally, and is connected to the crankshaft of the internal combustion engine by a connecting rod. The reciprocal movement of the piston is converted into the rotation of the crankshaft by the connecting rod.
The cylinder block is provided with a cylinder head, and a combustion chamber is disposed between the cylinder head and a head portion of the piston. The cylinder head includes an intake passage and an exhaust passage communicating with the combustion chamber. A throttle valve for controlling the amount of air flowing through the intake passage, and an injector extending to the combustion chamber so as to inject the fuel into the intake passage are disposed in the intake passage. The cylinder head has a spark plug for igniting a mixed gas in the combustion chamber.
During an intake process of the internal combustion engine, air is taken into the intake passage extending to the combustion chamber, fuel is injected from the injector, and the combustion chamber is filled with a mixed gas of air and fuel. Next, during a compression process of the internal combustion chamber, the mixed gas in the combustion chamber is compressed by the movement of the piston. The compressed mixed gas is ignited by the spark plug and explodes. The piston is moved in a direction opposite from the above direction by the force of the explosion, and the internal combustion engine is brought into an explosion process. Next, in an exhaust process of the internal combustion engine, the mixed gas in the combustion chamber is exhausted outside through the exhaust passage by the movement of the piston.
In recent years, a method for optimally controlling the air intake in the engine having the above configuration has been known in which a sub-throttle valve disposed in an intake passage is opened and closed according to the running state of the engine.
For example, Japanese Utility Model Application Laid-open Hei 3 No.116740 proposes an optimal air intake control method in which a first throttle valve and a second throttle valve are placed in an intake passage, and air control is performed based on the engine temperature. In this method, since the air intake control is executed with a bypass, it is possible to prevent the engine from stalling even during a cooling process in which the second throttle valve is completely closed.
Japanese Utility Model Application Laid-open Hei 5 No. 31231 proposes another method in which a first throttle valve and a second throttle valve are placed in an intake passage and are linked by a link mechanism, and the second throttle valve is forcibly and completely closed while the first throttle valve is fully opened. In this method, even when the first throttle valve drivingly connected to an accelerator pedal becomes out of control due to any trouble and is fully opened, the engine can be stopped by forcibly and completely closing the second throttle valve. This ensures safety.
In the above-described methods using the second throttle valve, a so-called sub-throttle valve, a motor is usually used as an actuator only for controlling the driving of the sub-throttle valve under the present circumstances.
The sub-throttle valve is effective in a running engine running state in which the main throttle valve is opened to a medium to high degree, but is not effective when the main throttle valve is closed.
A further method is known in which FID (first idling) during an engine cold start is performed while controlling the area of a bypass by coolant and wax. However, idling is performed while the rotating speed of the engine is maintained at a high level until the coolant temperatures rises, and this decreases controllability. Moreover, since it is necessary to ensure the bypass, the cost and weight are increased.
In a conventional engine in which a FID lever is manually operated during an engine cold start, the driver sometimes fails to return the lever, and performs normal operations in a FID state even after warming-up is completed. This is unfavorable for the engine and the environment.
The present invention has been made in view of the above drawbacks of the conventional arts, and an object of the invention is to provide an air intake control device of a fuel injection engine in which the first idling can be automatically controlled with a simple structure while controlling both the operation of a sub-throttle valve and the first idling during air intake control.
In order to achieve the above object, according to an aspect of the present invention, there is provided an air intake control device of a fuel injection engine having a fuel pump, an injector for injecting fuel from the fuel pump, and a throttle body in which the injector is mounted, wherein the throttle body includes a main throttle valve to be opened and closed in connection with the operation of a throttle grip by a driver, a sub-throttle valve to be opened and closed by a motor driving according to the running state of the engine, a driving rotator mounted at one end of a rotation shaft of the sub-throttle valve so as to corotate with the rotation shaft, a driven rotator for rotating a main throttle pulley for operating the main throttle valve, and a link mechanism for linking the driving rotator and the driven rotator, and wherein, when the sub-throttle valve is fully opened while the main throttle valve is closed, the rotation of the driving rotator is transmitted to the driven rotator by the link mechanism so as to rotate the driven rotator, and the main throttle valve is opened at a predetermined angle necessary for the first idling by the rotation of the driven rotator.
Preferably, the link mechanism includes a link member to be linked to the driving rotator, and an intermediate cam connected to the link member at one end and turnably mounted on the throttle body, and a part of the intermediate cam is contacted with the driven rotator so as to rotate the driven rotator.
Preferably, the driving rotator, the driven rotator, the link mechanism, and the main throttle pulley are placed on one side of the outer periphery of the throttle body, while a sub-throttle pulley for turning the sub-throttle valve, a driving motor for driving the sub-throttle pulley, and a throttle position sensor for detecting a rotation angle of the main throttle valve are placed on the other side.
Preferably, the engine further includes a coolant temperature sensor for detecting the temperature of a coolant for the engine, and an electronic control device for inputting a detected value from the coolant temperature sensor and controlling the opening and closing of the sub-throttle valve, and the electronic control device causes the sub-throttle valve to be fully opened for a predetermined period when the coolant temperature input when the engine is started is lower than a preset value.
Preferably, the engine is mounted in a motorcycle having a pair of main frames disposed on the right and left sides in the frame widthwise direction so as to extend rearward and diagonally downward from a head pipe of a frame, a cylinder head is placed between the main frames with an intake passage opening backward, and the driving motor for the sub-throttle valve is placed on the inner sides of the main frames behind the intake passage.
Preferably, the sub-throttle valve is placed on the upstream side from the main throttle valve in an air flow direction inside the throttle body.
According to the present invention, since the link mechanism is provided to link the main throttle valve and the sub-throttle valve, the main throttle valve can be opened at a small angle in a state in which the sub-throttle valve is fully opened during an engine cold start, and this allows the first idling to be automatically controlled. Consequently, it is possible to eliminate a choke valve, a choke lever, and an actuating cable used during an engine cold start in the conventional engine, and to prevent the choke from not being returned inadvertently.
By opening the main throttle valve at a small angle when performing a deceleration in a state in which the engine is being rotated at high speed, premixed air is prevented from being further enriched.
Since the link mechanism includes the link member to be linked to the driving rotator, and the intermediate cam linked to the link member and rotatably mounted on the throttle body, even when the driving rotator mounted on the sub-throttle valve shaft and the stopper cam for operating the main throttle pulley are apart from each other, the driving rotator can be prevented from being increased in size to be contacted with the stopper cam, by placing the intermediate cam linked to the link member between the driving rotator and the stopper cam in parallel. This makes it possible to improve the operability of the sub-throttle valve without decreasing the responsiveness of the sub-throttle valve.
Since the motor for driving the sub-throttle pulley and the throttle position sensor for the main throttle valve are placed on the same side of the throttle body, the components having harnesses can be collected, and the operability can be improved. Therefore, a harness is not placed on the side opposite from the side where the link member and the main throttle pulley are mounted. Moreover, since the components having a small outer shape can be collectively placed, the overall size of the throttle body can be reduced.
Since the coolant temperature sensor for detecting the temperature of the coolant for the engine and the electronic control device for controlling the opening and closing of the sub-throttle valve are provided, the first idling can be performed for a predetermined period after detecting the temperature of the coolant when the engine is started. This makes it possible to reliably improve the startability of the engine, and to prevent the choke from not being returned inadvertently.
In general, the cylinder head of the engine is the widest, and the space between the cylinder head and the main frames is small. Therefore, the main frames can be inhibited from being extended in the frame widthwise direction by placing the driving motor for the sub-throttle valve behind the cylinder head.
The amount of air intake can be reliably controlled by placing the sub-throttle valve on the upstream side in the air flow direction of the main throttle valve.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.